Resolving Conflicts between Irrigation Agriculture and Ecohydrology Using Many-Objective Robust Decision Making

Abstract

In arid regions, sustainable groundwater management is crucial for the protection of vulnerable local ecosystems but often leads to conflict with the interests of economic development. Management models containing simulation-optimization techniques are widely used to explore sustainable strategies of conjunctive water use, but previous studies often failed to address the system’s complexity as a whole, characterized by many stakeholders, a heterogeneous flow regime, and uncertain driving forces. This article contributes to a many-objective robust decision-making (MORDM) framework that integrates a state-of-the-art multiobjective optimization algorithm (MOEA) with robustness-based decision analysis to advance the field’s knowledge of conjunctive water use. The framework is applied to the trans-regional Heihe River Basin in China, which is facing a number of consequences of unsustainable water management, jeopardizing the downstream ecosystem and agricultural development in the river’s midreach. Results show that the current water management scheme is unsustainable in two respects: It overexploits groundwater resources locally and it cannot fulfill the minimum ecological outflow target. The baseline can be further improved with optimized solutions, but an unresolvable conflict exists between the required environmental outflow and water demand for the irrigated agriculture scheme under the current policy of inflow-proportional water sharing with the downstream. The robustness assessment highlights the key driving forces and how they shape the robustness of the system under different policies and changing conditions. The case study sheds light on the potential of MORDM to solve complex conjunctive water management problems and shows how it can help to improve understanding of the problem itself.